Rhys.Campbell, 0 means off since kernel version 3.5.
See reference here:
https://community.hortonworks.com/questions/71095/why-not-set-swappiness-to-zero.html
That's why most people use 1 (safe value)
Michael Caplan: please look at the size of your mysqld process in "ps
aux" command output. Due to overhead it might be actually bigger than
50G. I've checked settings we use in prod for MariaDB 10.1 on 64G
server and I set the buffer pool no bigger than 47G.
Regards
Le ven. 15 juin 2018 à 16:28, <Rhys.Campbell@xxxxxxxxxxxx
<mailto:Rhys.Campbell@xxxxxxxxxxxx>> a écrit :
My understanding is that the OS should never allocate swap when
swappiness is 0, so that has me confused.
0 doesn't mean off. If you really want to turn if off then see
swapoff / adjust your fstab.
1) How much of this is an OS issue vs MariaDB issue?
I'd say it's an application problem. You simply have more data
than RAM. In your case it might be more important to look at swap
in/out to see if your server is under pressure.
I would have a look at the innodb buffer pool page usage by
database / table to try and figure out what's being pushed into
swap and go from there.
http://www.youdidwhatwithtsql.com/innodbbufferpage-queries/2041/
-----Original Message-----
From: Maria-discuss [mailto:maria-discuss-bounces+rhys.campbell
<mailto:maria-discuss-bounces%2Brhys.campbell>=swisscom.com@xxxxxxxxxxxxxxxxxxx
<mailto:swisscom.com@xxxxxxxxxxxxxxxxxxx>] On Behalf Of Michael Caplan
Sent: 15 June 2018 14:48
To: Maria Discuss <maria-discuss@xxxxxxxxxxxxxxxxxxx
<mailto:maria-discuss@xxxxxxxxxxxxxxxxxxx>>
Subject: [Maria-discuss] Chewing Through Swap - Swappiness = 0
Hi,
I'm trying to figure out why my recently put into production
MariaDB is so swap hungry.
I'm running 10.2.14, with roughly 300GB data (1000K +/- tables).
95% tables are innodb. I have 64GB RAM, with INNODB buffer pool
size set to 50GB (full my.cnf below). The OS is Ubuntu 16.04.4.
This is a dedicated MariaDB server.
I have swappiness set to 0.
I started with available swap set to just shy of 1GB. When swap
got to 85% used, I bumped swap to 3GB. A day later, swap again
was 85% used, and I bumped it to 5GB. A day later, swap again was
85% used, so I bumped it to 15GB. 2 days later 50% of the
available swap was used. I restarted the DB moments ago, freeing
up all 15GB but 128MB of swap:
total used free shared
buff/cache available
Mem: 62G 20G 4.7G 266M
37G 41G
Swap: 14G 128M 14G
My understanding is that the OS should never allocate swap when
swappiness is 0, so that has me confused.
I've had similar issues with MySQL 5.6 (what I upgraded from) dipping
into swap, but that instance had swappiness set to 1, and never
consumed
more than 5GB of swap.
Questions:
1) How much of this is an OS issue vs MariaDB issue?
2) What MariaDB config vars should I be looking at to fix this issue?
3) What linux config vars should I be looking at to fix this issue?
Thanks,
Mike
[mysqld]
# GENERAL #
user = mysql
default-storage-engine = InnoDB
character-set-server = utf8
collation_server = utf8_general_ci
performance_schema = 0
max_allowed_packet = 16777216
sql_mode =
"NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
# MyISAM #
key-buffer-size = 32M
myisam-recover = FORCE,BACKUP
# SAFETY #
max-allowed-packet = 16777216
max-connect-errors = 1000000
skip-name-resolve
sysdate-is-now = 1
innodb = FORCE
local_infile = 0
secure_auth = 1
safe_user_create = 1
skip_symbolic_links = 1
wait_timeout = 28800
# DATA STORAGE #
datadir = /var/lib/mysql/
# BINARY LOGGING #
log-bin = /var/lib/mysql/mysql-bin
binlog_format = MIXED
server-id = 3
expire-logs-days = 7
sync-binlog = 1
# REPLICATION #
read-only = 1
skip-slave-start = 1
log-slave-updates = 1
relay-log = /var/lib/mysql/relay-bin
slave-net-timeout = 60
sync-master-info = 1
sync-relay-log = 1
sync-relay-log-info = 1
# CACHES AND LIMITS #
tmp-table-size = 32M
max-heap-table-size = 32M
query-cache-type = 0
query-cache-size = 0
max-connections = 500
thread-cache-size = 50
open-files-limit = 65535
table-definition-cache = 4096
table-open-cache = 10240
# INNODB #
innodb-flush-method = O_DIRECT
innodb-log-files-in-group = 2
innodb-log-file-size = 512M
innodb-flush-log-at-trx-commit = 2
innodb-file-per-table = 1
innodb-buffer-pool-size = 50G
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